All structural elements around your home’s living spaces should be insulated. It’s most practical to insulate many of these areas as part of a renovation. Otherwise, accessibility drives costs and determines what’s worth doing.

Insulation is rated by its resistance to heat flow—or R-value. The higher the R-value, the greater the resistance. If you double the R-value by adding insulation, you halve heat loss in the insulated area.

Installers recommend a product based on where it’s to be installed, their experience with the product, and their relationships with their suppliers. Here’s a roundup of the most popular types of insulation and materials.